SDK lifecycle hooks

[AbhiPrasad]

Problem Statement

In order to integrate with profiling, the SDK needs to expose a couple of new lifecycle hooks. Primarily we need hooks on startTransaction, and transaction.finish() so that profiling can start/end profiles.

Replay also needs something similar, but centered around [TBD FILL THIS IN]. For now we aim not to solve for the Replay case specifically, but we should keep it in mind.

Solution Brainstorm

Let's introduce hooks to the Sentry client. These live on the client and as stored as simple function pointers.

type Hook = Record<KnownHooks, Function[]>;

^ The type above prob needs to actually be a union or overload of some sort so we get better intellisense, but our TS version might hold us back from it 😭.

Whenever we need to add a hook, we access the client, and call `client.on('...');

Whenever a hook is called, we call client.emit('...'), which will iterate through the array of hooks and call them all one at a time.

This is special case - but we need this to unblock profiling so let's . We keep these APIs completely internal, we can change it later on.

• Add hook interface to BaseClient and Client type #7343
• feat(core): Emit hooks for transaction start/finish #7387

Stretch

Send profiling + transactions in the same envelope

• profiling stops first when transaction is finished
• we need some way to combine envelopes (createEnvelope) in transaction.finish

[AbhiPrasad]

Based on whatever we do here - we can update getsentry/rfcs#34 accordingly, but let's try to solve this for JavaScript first, and then try to generalize. We can always fix inconsistencies with v8.

[mydea]

👍 For replay, we'd love to have something like:

• onBeforeSend
• and/or onAfterSend

We can add them as follow-up steps, should be straightforward once the general setup is there 🚀